It is conventional that deep-well pumps are driven by a drive. If the drive is realized as an electric drive, the effective power of the drive is able to be recorded. If the effective power has a negative preceding sign, the drive operates as generator, and a positive preceding sign means that the drive operates as a motor. The drive, for example, can be implemented as a gear unit which is drivable by an electric motor. A change between motor and generator operating modes triggers a teeth flank change of the gear teeth components of the gear unit, which reduces the service life.